1. Field of the Invention
The present invention relates to a method and an apparatus for monitoring a road, and more particularly, to a method and an apparatus for monitoring a road wherein road information, such as a distance to a preceding vehicle, is acquired using a picture captured by a camera.
2. Description of the Related Art
Recently, an unmanned vehicle, which perceives driving circumstances and automatically controls driving performance, has been under development. Such an unmanned vehicle usually includes a lane marker detector for detecting lane markers to be used for keeping the unmanned vehicle running in the same lane, and a vehicle detector for detecting a preceding vehicle in order to prevent the unmanned vehicle from bumping the preceding vehicle.
The lane marker detector detects lane markers from a picture captured by an input apparatus such as a camera, such that the road on which the unmanned vehicle is running can be modeled.
Marking objects disposed on the road according to a predetermined scheme are detected for modeling of the road, and a typical example of the marking objects is a lane marker.
The lane marker detector, including a camera for capturing a forward picture, usually perceives lane markers from the captured picture based on a brightness difference between a road surface and the lane markers because the lane markers are brighter than the road surface.
The vehicle detector detects a preceding vehicle by various methods.
One example of these is a stereo camera method, where a distance to a preceding vehicle is calculated based on an angular difference of two cameras aiming at the preceding vehicle.
A laser radar method and a mm-wave (electromagnetic wave whose wavelength is of an order of magnitude of millimeters) radar method are also used to detect a distance to a preceding vehicle, and in such methods, a reflective wave reflected from the preceding vehicle is detected and used for calculating the distance.
As described above, according to the prior art, an unmanned vehicle must be equipped with two different apparatus, a lane marker detector and a vehicle detector for distance control of the vehicle.
Therefore, it is obvious that the cost for realizing an unmanned vehicle must be reduced if there is provided a method for calculating a distance to a preceding vehicle from a captured picture.
Moreover, the stereo camera method has difficulty in setting of the two cameras, the laser radar method is apt to lose reliability because a laser ray is too narrow and easily scattered by moisture in the air, and the mm-wave radar is very expensive.